Aims To estimate changes in the substance use behaviors of patients who received services as part of the US Substance Abuse and Mental Health Services Administration's (SAMHSA) Screening, Brief Intervention and Referral to Treatment (SBIRT) grant program. Methods We use a pre-post design and performance monitoring data collected by SBIRT organizations. For a sample of 17 575 patients, we compare pre-SBIRT substance use with substance use 6 months after receipt of SBIRT services. SBIRT's correlation with changes in substance use was estimated using generalized linear mixed models to account for the clustering of patients within health-care facility and US state. Results From pre-to post-SBIRT we found large and statistically significant decreases for almost every measure of substance use. Model-adjusted means indicate that the prevalence of alcohol use was lower 6 months later by 35.6%, heavy drinking by 43.4% and illicit drug use by 75.8%. Greater intervention intensity was associated with larger decreases in substance use. The study design does not support causal conclusions and estimated decreases in reported substance use are due, at least in part, to a well-known set of confounders and natural substance use patterns that may be unrelated to any particular SBIRT intervention.Conclusions Compared with previously published findings on the Screening, Brief Intervention and Referral to Treatment grant program, our estimates of substance use reduction were smaller, but still consistently large in absolute magnitude and within ranges of estimates from past trials of Screening, Brief Intervention and Referral to Treatment.

Honeybee colonies are highly integrated functional units characterized by a pronounced division of labor. Division of labor among workers is mainly age-based, with younger individuals focusing on in-hive tasks and older workers performing the more hazardous foraging activities. Thus, experimental disruption of the age composition of the worker hive population is expected to have profound consequences for colony function. Adaptive demography theory predicts that the natural hive age composition represents a colony-level adaptation and thus results in optimal hive performance. Alternatively, the hive age composition may be an epiphenomenon, resulting from individual life history optimization. We addressed these predictions by comparing individual worker longevity and brood production in hives that were composed of a single age cohort, two distinct age cohorts, and hives that had a continuous, natural age distribution. Four experimental replicates showed that colonies with a natural age composition did not consistently have a higher life expectancy and/or brood production than the single cohort or double cohort hives. Instead, a complex interplay of age structure, environmental conditions, colony size, brood production, and individual mortality emerged. A general trade-off between worker life expectancy and colony productivity was apparent, and the transition from in-hive tasks to foraging was the most significant predictor of worker lifespan irrespective of the colony age structure. We conclude that the natural age structure of honeybee hives is not a colony-level adaptation. Furthermore, our results show that honeybees exhibit pronounced demographic plasticity in addition to behavioral plasticity to react to demographic disturbances of their societies.

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